Image processing
4.1 Reading code (1D and 2D codes)
SIMATIC MV420 / SIMATIC MV440
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Operating Instructions, 04/2013, A5E02371045-06
4.1.2.4
Performance characteristics when reading PDF417 codes
Note
Unsupported code types
The following code types are not supported: Truncated PDF417, Macro PDF417, Micro
PDF417.
Note
Changing the time-saving image acquisition with half resolution
With bar widths > 6 pixels, change to time-saving image acquisition at half resolution. This
change is also useful at high object speeds.
The recognition processes of the reader allow reliable and fast reading of printed PDF417
codes of good quality.
Range of application
●
The codes can have any alignment in the image.
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The code can be printed both dark on a light background and light on a dark background.
●
Codes with a bar width ≥ 3 pixels and in which the height of a single row of symbols is ≥ 9
pixels can be read.
●
The width of the black and white bars must be uniform over the entire code field.
●
The viewing angle of the sensor to the surface can be between 70° and 90°.
●
The code should not make contact with any other objects in the image, you can do this,
for example by keeping the quiet zone free with twice the column width.
●
Within the code, the ratio of contrast (in other words, the difference between black and
white) to noise should be at least three. This ratio must be similar over the entire code
field.
●
The image background must have a homogeneous brightness, for example no texture
such as stripes.
●
The error correction codes (in other words, the lower part of the barcode) must not be
covered.
●
At the minimum bar width, each symbol column requires 51 pixels. Along with the four
start and stop patterns, the width of the code with n code columns is at least: Width = 51 *
(n + 4) pixels.
Due to the limited image resolution, codes can be read as follows:
–
with the SIMATIC MV440 SR reader up to 40 code rows and up to 6 code columns.
–
with the SIMATIC MV440 HR reader up to 60 code rows and up to 12 code columns.
Summary of Contents for SIMATIC MV420
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